Xenon binding energy

Hermans, J., Subramaniam, S. The free energy of xenon binding to myoglobin from molecular dynamics simulation. Isr. J. Chem. 27 (1986) 225-227... 

Praseodymium oxychloride produced from praseodymium chloride with a pretreatment in oxygen followed by methane conversion in the presence of feedstream TCM (as shown in Figure 3) displayed an O Is peak at 529.0 eV but no shoulder. The peak position did not change after xenon-ion sputtering. The spectra for Pr 3d were similar to those for other praseodymium oxychloride samples. The binding energy of Cl 2p was 198.9 eV while the peak had a shoulder at 200 eV. The shoulder disappeared after the sputtering. 

Shifts of Xenon 3ds/j Binding Energies Relative to That of Xe (eV) XeFi 2.87 =t 0.02... 

The shifts of the xenon 3d./, binding energies are, with one exception, well within experimental error of the values determined by Karlsson, Siegbahn, and Bartlett. For XeF, we have found a value of 7.64 0.04 eV compared with their value of 7.88 0.18, the difference being only sightly more than the combined uncertainties. 

There are two predominant challenges to direct observation of alkanes coordinated to transition metals (1) the short-lived nature of metal/alkane complexes and (2) competition for coordination of the alkane to the metal center. Because of the weak binding energy, alkane coordination is typically short-lived. Thus, fast spectroscopy techniques are required, and these techniques are often coupled with low temperatures in order to slow processes that result in alkane dissociation. In addition to the rapid dissociation of alkanes, most organic substrates will effectively compete (kinetically and thermodynamically) with alkanes for coordination to metals. Thus, the reaction medium is an important consideration since most common solvents are better ligands than alkanes, and attempts to observe alkane coordination have been commonly performed in the gas phase, in hydrocarbon matrices, or in liquid krypton or xenon. Finally, photolysis is generally required to dissociate a ligand at low temperature to create a transient coordination site for the alkane. 

At 20°K the mobility of adsorbed xenon should be limited, and differences in binding energy on the surface thus should no longer influence the distribution of adsorbate over the emitter. As is apparent from Fig. 49, adsorption on a liquid hydrogen cooled emitter initially raises the emission everywhere except for the high index planes, which... 

The observations in the field emission microscope establish that under the conditions of the adsorption studies of Section II, C, 1, a, xenon was mobile, and that the binding energy varies with the crystal orientation. The structure of the filament surface is not known in detail however, this is a polycrystalline specimen, the cylindrical surfaces of which are made up of planes with the orientation (hhk). The condensation coefficient must therefore be an average quantity, and energy transfer may thus not be the limiting step. 

In the adsorption experiments, only a small portion of the surface was filled when brought to a steady state at p = 10-7 mm. If this concentration were to correspond to saturation of the entire surface the xenon adsorbed would have a cross-sectional area of 50A2, more than three times the gas kinetic value. A more reasonable view is that only the rougher, stepped planes are filled. From the calculated binding energy ratios which appear in fair agreement with experimental results found by field emission for the 111 and 130, we can estimate for Xe a heat of 5.4 kcal/mole on the 100 and 4.5 kcal/mole for the 110 plane. 

Under the conditions of the rate experiments evaporation was found to be appreciable for xenon held with a binding energy of 6 kcal/mole. During a run (p < 5 x 10 9 mm) the 110 planes should, therefore, have a cover of less than 1011 atoms/cm2, the 11 l s less than 5 x 1012. This is also consistent with the direct observation of the 111 planes in the field emission microscope—at pressures comparable to those in the adsorption experiments the 111 was occupied at 79°K, but not at 85°K. 

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